Enzymes

Lesson Starter

With the person next to you, try and think of as many CHEMICAL

REACTIONS as you can.. (write these down in a spider

diagram in your jotter)

Common Chemical Reactions

Photosynthesis Fireworks Digestion

Striking a match Baking a cake Starting a car

What is a chemical reaction?

What is a chemical reaction?

A process in which one or more substance (reactants) is chemically changed into one or more

new substance (product)

Reactants Product

Chemical Reactions•The speed that a reaction occurs at is called the REACTION RATE•Most chemical reactions occur very slowly at normal temperatures•We can increase the speed of a chemical reaction

Increasing reaction rate•Increasing temperature•Increasing concentration of a reactant•Breaking down solids into smaller pieces

USING A CATALYST

Investigating Catalysts

Hydrogen peroxide (H2O2) is a harmful liquid which (under normal conditions) will very slowly break down into water

(H2O) and oxygen

Experiment: AIM•We are going to carry out an experiment which will:

Investigate the effect of using a catalyst on the decomposition rate of hydrogen peroxide

Method•Set up two test tubes in a test tube rack•Into both test tubes pour in some hydrogen peroxide•Into one of tubes add a small quantity of manganese dioxide•The other test tube will be a CONTROL Hydrogen

peroxide

Small quantity of manganese dioxide

The importance of a control•A control is a copy of the experiment in which all factors are kept exactly the same except for the one being investigated in the original experiment – In this case the use of the catalyst•When 2 results are being compared, any difference found between the two must be due to that one factor.

Method•Set up two test tubes in a test tube rack• Into both test tubes pour in some hydrogen peroxide• Into one of tubes add a small quantity of manganese dioxide•The other test tube will be a CONTROL•Note down your observations in your book•Test the gas given off using a GLOWING splint

Hydrogen peroxide

Small quantity of manganese dioxide

Observations

Conclusion•The tube with manganese dioxide added produced bubbles•Adding the manganese dioxide increased the rate at which bubbles were produced

•Oxygen was present as the glowing splint relit

What are Catalysts•Substance which INCREASES the rate of a chemical reaction•They are NOT CHANGED or USED UP in the reaction (reusable)•They LOWER the energy needed to kick start the reaction

Uses of catalysts•Modern cars have a catalytic converter to help

reduce the production of toxic gases.• Catalytic converters use a platinum and

rhodium catalyst • Increases the speed that (harmful) carbon

monoxide and unburnt fuel (from the exhaust) reacts with oxygen from the air- help protect the environment• The catalysts are designed to work best at the

high temperatures found in the engine.

Task: Write a report•Aim of the experiment•Method- A step by step guide to what you did (including control and why). Include diagrams•Results- what did you see happening in both test tubes? •Conclusion- why did you see what you did? What did the manganese do? What is manganese?• Information about catalysts- what is a catalyst? Why is it useful? Where are catalysts used in every day life?